Tilting mechanisms for the seat of a chair are well known. Typically, such mechanisms allow only rearward tilting and employ an adjustable spring-like mechanism to return the seat to a generally horizontal position when the chair is not in use. Chairs such as these are in common use and have the advantage, over rigid chairs, that the occupant may shift his position in order to transfer the pressure of sitting from one part of his anatomy to another. This shifting is found to be relaxing and aids in postponing or even preventing tension and fatigue.
Improvements over rearward tilting are to be found in U.S. Pat. No. 1,678,668 (Collier) wherein there is disclosed a chair tilting mechanism which tilts forwardly as well as rearwardly and in U.S. Pat. No. 1,723,415 (Ferris) wherein there is disclosed a chair tilting mechanism which is capable of a limited lateral rocking or tilting movement.
Further improvements allowing omnidirectional tilting of chair mechanisms are described in U.S. Pat. Nos. 2,048,148 (Stoll), 4,099,697 (Von Schuckmann), 4,185,803 (Kalvatn), 4,431,157 (Arild) and 4,498,656 (Arild).
The Stoll patent discloses a ball joint surrounded by a coil spring held in compression between a flange and a seat mounted swivel bearing. A stub shaft extends between the ball and the swivel bearing, so that as the occupant's weight is shifted on the seat, tilting can occur in any direction. As soon as the lateral thrust force is relieved, the seat will return to its neutral, home position. This mechanism may be interposed between a standard pedestal tube and the chair seat.
In the Von Schuckmann patent the omnidirectionally tilting mechanism must be located in a uniquely constructed base support structure. It comprises a ball received in a socket :for universal movement with a shaft secured to and extending from the ball. A star-like array of generally radial tension springs is attached to the shaft and yieldably resist deflection of the shaft out of its normal position in all directions.
The patented Kalvatn mechanism comprises a pair of concentric rings which are mutually moveable, each about a torsion bar. Its universal tilting mechanism may also be mounted between standard chair seats and pedestals.
Similarly, in each of the Arild patents there is disclosed a tilting mechanism comprising a pair of torsion bar elements mounted upon yokes disposed normally to one another. These mechanisms also may be mounted between standard chair seats and pedestals.
Although, as noted, it is possible to interpose several types of the known omnidirectionally tiltable chair support structures between standard seats and seat supports, they are all of a size and complexity which require extensive modifications to existing chair structures for their incorporation therein. Thus, their interposition is not only impractical but the appearance they present is unsightly.
In a related patent, U.S. Pat. No. 4,807,841, "Omnidirectionally Tilting and Swivelling Support Mechanism for Chairs or the Like" (Edstrom) herein fully incorporated by reference, I have disclosed a structure which relies upon flexurally distorting a control shaft. The dimensions of the mechanism allow it to be mounted totally out of sight, completely within a standard tubular chair support pedestal.
It is an object of the present invention to provide an improved omnidirectional tilting mechanism, utilizing flexure members, interposable between a support structure and a supported structure, which allows self righting, relative tilting movement between these structures over a full 360 degrees and has a low profile, allowing it to be mounted unobtrusively between these structures. When incorporated into a chair, it may be disposed upon any standard pedestal shaft (including those incorporating a gas powered lift therein), or ether type of seat support for supporting any standard seat, without detracting from the functionality of either the support or the seat.